Iraqi Journal of Chemical and Petroleum Engineering Vol.16 No.2 (June 2015) 9- 17 ISSN: 1997-4884 Furfural Degradation in Waste Water by Advanced Oxidation Process Using UV/H2O2 Awatif S. Alsaqqar * , Mohammed Sadeq Salman ** , Waleed. M. Abood *** And Dhafer F. Ali *** * Department of Civil Engineering / College of Engineering / Baghdad University ** Avi-Cenna E-learning Center / Baghdad University *** Ministry of Industry and Minerals / Commission of Research and Industrial Development/ Solar and Environment Researches Centre Abstract Furfural is one of the one of pollutants in refinery industrial wastewaters. In this study advanced oxidation process using UV/H2O2 was investigated for furfural degradation in synthetic wastewater. The results from the experimental work showed that the degradation of furfural decreases as its concentration increases, reaching 100% at 50mg/l furfural concentration and increasing the concentration of H2O2 from 250 to 500 mg/l increased furfural removal from 40 to 60%.The degradation of furfural reached 100% after 90 min exposure time using two UV lamps, where it reached 60% using one lamp after 240 min exposure time. The rate of furfural degradation k increased at the pH and initial concentration of furfural decreased, but different H2O2concentrations indicated no significant effects on the reaction rate. UV/H2O2 process is effective for furfural degradation in wastewater at neutral pH where the disposal of such effluents will be within the environmental limitations. Key Words: Furfural, UV/H2O2, Degradation, AOP. Introduction Today water pollution is one of the most important environmental problems in the world. Industrial wastewaters containing toxic chemicals are the main sources for such problems. Petroleum refinery effluents are priority pollutants due to their high polycyclic aromatics content, which are toxic. They encompass a wide range of contaminants at varied concentrations that are harmful. Large amounts of water are used in petroleum refinery and significant volumes of wastewater are generated (0.4 – 1.6 times the amount of the crude oil processed) which need to be treated before disposal to water bodies [1, 2]. Among these contaminants found in petroleum refinery effluents is a compound known as furfural. Furfural is a toxic aromatic aldehyde with the chemical formula C4H3OCHO. It is pale yellow or colorless oily liquid and turns into brown or red in the presence of air or light [3, 4]. Furfural production is from a mixture of plant raw material (i.e corn seed hulls, cane bagasso and residues of olive extraction) with dilute sulfuric acid (acidic hydrolyaztion).Furfural is then Iraqi Journal of Chemical and Petroleum Engineering University of Baghdad College of Engineering Furfural Degradation in waste water by advanced oxidation process using UV/H2O2 10 IJCPE Vol.16 No.2 (June 2015) -Available online at: www.iasj.net recovered by steam distillation and fractionation with (98-99) % purity [5]. The main use of furfural is in the form of feed stock for furfural alcohol (FFA) this is used as an input for furan resin that is used for foundry binders[6]. Furfural and FFA are consumed by chemical industries as intermediate products such as nylons, lubricants and solvents, adhesives, medicines, plastics, urea furan resin synthesis; precision casts and dies [6]. Furfural is used as a solvent which has a high capability for separation of multi- components especially in the petroleum industry to separate sulfur and carbonaceous compounds [3]. Acute health effects (short-term) may occur shortly after exposure to furfural which may irritate the skin and eyes. Breathing furfural may irritate the nose and throat, also the lungs causing coughing and/ or shortness of breath. Higher exposure can cause fluid buildup in the lungs. High concentrations of furfural may cause the person to be dizzy, light headed and to pass out. The chronic health effects (long-term) may occur at some time after exposure to furfural and can last for months or years. This may cause skin itching and skin rash (skin allergy). Repeated exposure may cause loss in taste sense, numbness of the tongue, headache, tiredness, itchy throat, watery eyes and also may cause liver damage [4, 6, 7].Furfural is a very slow biodegradable material (27X 10 -7 g/g biomass) which means that it has significant effects on the aquatic life and fishes [8]. The presence of furfural increase the toxicity of industrial effluents and its removal may be difficult or impossible by conventional treatment processes used in most industries. Many technologies have been developed to treat effluents containing furfural. Basheer et al., (2011) reviewed that petroleum refinery effluents were treated by coagulation, chemical oxidation, adsorption, biological techniques, membrane filtration and catalytic wet air oxidation [1]. Belay et al. (1997) investigated the metabolism of furfural by Methanococcus delta under anaerobic conditions; the results showed the ability of these micro organisms to transfer furfural to furfural alcohol [8]. Hassan et al. (2012) used activated sludge to provide micro organisms for furfural degradation [3]. Sulaymon and Abood, (2005) tested adsorption of furfural onto activated carbon [9], where Ghazi, (2012) used agricultural waste for furfural adsorption [6]. Sulaymon and Hayfa, (2014) used activated carbon and dead micro organisms from anaerobic sludge for adsorption/biosorption of furfural [10]. All these methods transfer the contaminants from one media to another therefore a second treatment process is required to eliminate these contaminants. Several solutions have been proposed and compared with these traditional methods. In recent years the application of photo catalysis technique in wastewater treatment was tested. These techniques are known as advance oxidation processes (AOPs) which can completely degrade organic pollutants into harmless inorganic substances like CO2 and H2O under moderate conditions [2]. These processes are widely used in the decomposing of organic products in industrial wastewater and groundwater owing to their complete mineralization, produce no sludge, high reaction rates and operate under ambient temperature and pressure conditions [1, 8, 11, 12, 13]. AOPs are defined as potential processes that are capable of producing hydroxyl radicals ( • OH), which are extraordinary reactive oxidations (oxidation potential 2.8 V) in sufficient Awatif S. Alsaqqar, Mohammed Sadeq Salman , Waleed. M. Abood And Dhafer F. Ali -Available online at: www.iasj.net IJCPE Vol.16 No.2 (June 2015) 11 quantity for mineralizing a majority of complex organic materials to carbon dioxide, water and inorganic ions. Majority of AOP processes like cavitation, photo catalytic oxidation and Fenton chemistry are performed by applying various combinations of homogeneous photo Fenton (Fe III), Ozone and TiO2 such as UV/O3, UV/H2O2, UV/H2O2/O3, O3/TiO2, TiO2/H2O2/O3 and more. These combinations use energy to produce highly reactive intermediaries with high oxidation or reduction potential. The hydroxyl radicals may be obtained from powerful oxidants, such as H2O2 and O3, combined with irradiation.[2,13, 14, 15]. Basheer et al. (2011) summarized several treatment producers for petroleum refinery effluents using AOPs; it was observed that the reduction in COD and DOC may reach 90% [1]. Kang et al. (2009) used UV/O3 for the degradation of furfural wastewater. They achieved complete degradation within 3 hr under optimum conditions [13]. Nevak (2010) applied Fe(III)/H2O2/solar-UV process to petrochemical refinery wastewater, the reduction in COD reached 49% after 8 hr of exposure to solar radiation [2]. The objective of this study is to describe experimentally the feasibility of furfural removal from synthetic wastewater by UV/H2O2technology under different operational conditions, Furfural initial concentration, H2O2 dosage, number of UV lamps used and pH of the solution. Experimental Work Synthetic wastewater containing different concentrations of furfural was tested by UV/H2O2technology under different operational conditions in a photo reactor. 1- Materials A. Furfural (C4H3OCHO) has a chemical structure shown in Fig. (1), of molecular weight 96.06 gm/mol, has synonyms of 2- furaldehycle, Furyl and 2 Furyl methanol [7].The physical properties of furfural are listed in Table (1). Fig. 1, Chemical structure of furfural [9] Table (1), Recorded Physical properties of Furfural [9] Color Colorless to yellow and red-brown when exposure to light and air Odor Aromatic odor as benzaldehy de Specific gravity 20 o C 1.1598 Flash point, open cup o C 68.3 Heat of vaporization (kcal/mol) at 160 o C 9.22 Heat of combustion (kcal/mol) 560.2 Lower explosive limit in air at (125 o C) vol.% 2.1% Ignition temperature o C 39.3 Furfural Degradation in waste water by advanced oxidation process using UV/H2O2 12 IJCPE Vol.16 No.2 (June 2015) -Available online at: www.iasj.net B. Hydrogen peroxide (H2O2) 50% w/w was obtained in a plastic container of molecular weight 34.01 g/mol supplied by GCC Company. The stock solution is to be diluted by distill water for the preparation of different concentrations used in the tests. 2- Photo reactor units A glass container 3 Liter in volume was used as the photo reactor. It is provided witha cooling jacket and a flexible sealed cover (rubber) with holes; two for UV lamps (model no. 5212RL manufactured by Sterilight copper company), one hole for supplying air and another for a thermometer. Sampling was achieved from a bottom valve as shown in Fig. (2) for interval times (30, 60, 90,120,180 and 240 min). Experiments were carried out at different operational conditions, furfural concentration (300, 200, 100 and 50) mg/l, H2O2 dosage (1000, 750,500 and 250) mg/l, UV lamps (one and two lamps) and pH solution (3, 7.5 and 11). Fig. 2, Schematic representation of the photo reactor 3- Analyses method For the determination of furfural concentrations in a solution, two methods that could be used: the colorimetric analyses by using a spectrophotometer at wave length 430 nm [16]. Another method using HPLC (High Performance Liquid Chromatography) was used. In this study HPLC (type CECIL, UK) was used for furfural concentration determination with operation conditions listed below [17]. Mobile phase : 5% acetic acid w/v in water methanol (80:20) Column : C 18 (5 µm) Flow rate : 1 ml/min Injection volume : 285 nm 4- Removal Determination Percentage of furfural removal was determined using eq.(1). % Removal = … (1) Where: Co is furfural initial concentration and Ct furfural concentration at time t during the treatment process. Kinetic rate model The progress of the reaction is observed to take place in a completely mixed batch reactor (CMBR), as complete mixing occurs uniformly throughout the reactor with an identical reaction rate (k).Common kinetic rate expressions can be evaluated to determine the correlation between the experimental data and the reaction kinetics. Most of the degradation processes follow a first order reaction [18] as expressed in eq. (2): … (2) Where: k= first-order rate constant,t -1 Integrating this eq. (2) yields to … (3) Awatif S. Alsaqqar, Mohammed Sadeq Salman , Waleed. M. Abood And Dhafer F. Ali -Available online at: www.iasj.net IJCPE Vol.16 No.2 (June 2015) 13 Taking the natural logarithm of eq. (3)will obtain the following relationship: ln(Ct) - ln(Co) = -kt … (4) For a first-order reaction, the plot of ln(Ct) as a function of t, as shown in eq. (4), will result in a linear relationship. Results and Discussion 1- Effect of Initial Furfural Concentrations Four initial furfural concentration were investigated (50, 100, 200 and 300) mg/l at pH 7.5, H2O2 dosage 500 mg/l and one UV lamp. Fig. 3, Removal efficiencies of furfural at different concentrations for H2O2=500mg/l, 1 UV lamp and pH=7.5 The results in Fig.(3) show that the degradation of furfural decreases as its concentration increases, reaching 100% at 50mg/l furfural concentration at 120 min, but did not exceed 50% at 200 and 300 mg/l at 240 min. The dosage of 500mg/l H2O2 provided enough • OH radicals for complete degradation of 50 mg/l furfural but was not enough for the degradation of 200- 300 mg/l. The use of H2O2 is more efficient in the presences of high concentrations of organic compounds (furfural), because the organic matter competes better with H2O2for the generation of • OH radicals [19]. From these results the optimum H2O2 dosage could be determined for economical purposes. 2- Effect of H2O2 dosage Fig (4) shows the effect of various H2O2 concentrations (250, 500, 750 and 1000) mg/l on the furfural removal efficiency. Increasing the concentration of H2O2 from 250 to 500 mg/l increases the furfural removal from 40 to 60%.At higher concentrationsH2O2 will absorb more UV that will produce more •OH radicals which will degraded more furfural. But overdosing of H2O2 (more than 500mg/l) may cause simultaneous reactions that could: consume H2O2 or cause self decomposition of H2O2 to oxygen and water where this will reduce the generation of • OH radicals. It is also observed that the reaction of • OH with excess H2O2willform weak radicals • HO2 (hydroperoxyl with oxidation potential 1.7 V). Hydroperoxyl radicals may react with H2O2 to produce also water and oxygen. So these radicals (•OH and • HO2) will act as inhibiting agents and the removal efficiency of furfural decreases [20].These reactions are shown in the following equations: H2O2 + hυ (UV energy) → 2 • OH H2O2 + • OH→ • HO2+ H2O H2O2+ • HO2→ • OH +H2O +O2 2 • OH → H2O2 2 • HO2→ H2O2 +O2 • OH + • HO2→ H2O2+ O2 0 20 40 60 80 100 120 0 30 60 90 120 150 180 210 240 R e m o v a l E ff ic ie n ce % Time (min) 300 mg/l 200 mg/l 100 mg/l 50 mg/l Furfural Degradation in waste water by advanced oxidation process using UV/H2O2 14 IJCPE Vol.16 No.2 (June 2015) -Available online at: www.iasj.net Fig. 4, Removal efficiencies of furfural at different H2O2 concentrations for furfural concentration= 200 mg/l, 1UV lamp and pH=7.5 3- Effect of Light Intensity Fig. (5), shows the effects of light intensity on the degradation of furfural. The intensity of light was adjusted by using one or two lamps at constant furfural concentration of 200 mg/l, H2O2 dosage 500 mg/l and pH 7.5. As the intensity of light increased, the removal of furfural accelerated because more light intensity is available and more • OH radicals are produced under the action of UV/H2O2. Fig. 5, Effect of UV intensity on removal efficiency of furfural 200 mg/l in concentration, H2O2 =500mg/l and pH=7.5 The rate of photolysis of H2O2 depends directly on the incident power. At low UV power the photolysis of H2O2 is limited. While, at high UV power more • OH radicals are produced upon the photo dissociation of H2O2, hence furfural removal rate increases. It appears that the UV power lies within the linear range and hence all the photons provided were effectively used [21]. The degradation of furfural reached 100% after 90 min exposure time using two UV lamps, where it reached 60% using one lamp after 240 min exposure time. 4- Effect of Ph Fig. (6) shows that the degradation rate of furfural was higher in acidic solution pH 3 (about 80% furfural removal).This pH value was the best for the UV/H2O2 process as • OH radicals are free for reaction. At high pH values OH - ions will increase in the solution and may react with • OH radicals where this will decrease furfural degradation. Also in alkaline medium the oxidizing species hydroperoxy anion (HO2  ) are formed and these anions react with • OH radicals and residual H2O2 consequently lowering the removal rate of furfural. Hydrogen peroxide is most stable in the pH range 3-4, but its decomposition rate rapidly increases with increasing pH above pH 7.5 [21]. Fig. 6, Effect of pH on removal efficiency of furfural= 200 mg/l, 1UV and H2O2= 500mg/l 0 20 40 60 80 100 0 30 60 90 120 150 180 210 240 R e m o v a l E ff ic ie n ce % Time (min) 1000 mg/l H2O2 0 20 40 60 80 100 120 0 30 60 90 120 150 180 210 240 R e m o v a l E ff ic ie n ce % Time (min) 1 UV 2 UV 0 20 40 60 80 100 120 0 30 60 90 120 150 180 210 240 R e m o v a l E ff ic ie n ce % Time (min) pH=3 pH=7.5 pH=11 Awatif S. Alsaqqar, Mohammed Sadeq Salman , Waleed. M. Abood And Dhafer F. Ali -Available online at: www.iasj.net IJCPE Vol.16 No.2 (June 2015) 15 All the results in section 4 were at pH 7.5 and not 3. From these results furfural removal was observed at pH 7.5. Hence this could be considered if real wastewaters are to be treated by this process. No need to add chemicals to the wastewater to decrease its pH for furfural degradation. The wastewater then will be discharged to water bodies at neutral pH which is recommended for effluents disposal. 5- Kinetic Results Eq. (4) was applied for all of the experimental results to find the rate of reaction (degradation of furfural by UV/H2O2). A plot of ln Ct/Co vs. time is illustrated in Fig. (7). The slope of the line in this plot is equal to the first- order rate constant k and the intercept is equal to In (C0). The calculated values of k (min -1 ) for the different operation conditions are listed in Table (2). Fig. 7, First order Rate Constant of Furfural Removal by UV/H2O2 at 100 mg/l concentration, 500 mg/l H2O2 and 1 UV Table (2) First Order Rate Constant k min -1 at Different Operation Conditions Exp. pH Furfural Conc. mg/l H2O2mg /l No. of UV lamps kmin -1 R 2 1 3 200 500 1 0.007 0.905 2 7.5 200 500 1 0.0034 0.894 3 11 200 500 1 0.0024 0.652 4 7.5 200 500 1 0.0034 0.8937 5 7.5 300 500 1 0.0037 0.817 6 7.5 100 500 1 0.0077 0.902 7 7.5 50 500 1 0.0183 0.995 8 7.5 200 1000 1 0.0026 0.995 9 7.5 200 750 1 0.0026 0.705 10 7.5 200 500 1 0.0034 0.894 11 7.5 200 250 1 0.0024 0.894 12 7.5 200 500 2 0.0257 0.933 0 0.5 1 1.5 2 0 30 60 90 120 150 180 210 240 270 300 ln ( C t/ C o ) Time (min) y=0.007x+0.358 R2=0.902 Furfural Degradation in waste water by advanced oxidation process using UV/H2O2 16 IJCPE Vol.16 No.2 (June 2015) -Available online at: www.iasj.net Table (2) shows that the rate of furfural degradation k increases as the pH decreases, 0.007, 0.0034 and 0.0024min -1 for pH 3, 7.5 and 11 respectively. For different furfural initial concentrations the rate of degradation increased k 0.0037, 0.0034 0.0077 and 0.0183min -1 as the initial concentration of furfural decreased (300, 200, 100 and50) mg/l where k was nearly the same for 200- 300 mg/l furfural initial concentration. The k values using different dosages of H2O2were 0.0024, 0.0034, 0.0026 and 0.0026 min -1 for 250, 500, 750 and 1000 mg/l respectively, indicating no significant effects on the reaction. All the above results had been achieved using one UV lamp, the k value increased using two UV lamps to 0.0257 min -1 which is higher than k value 0.0034min -1 using one UV lamp for the degradation of 500 mg/l furfural concentration Conclusions 1- The degradation of furfural decreases as its concentration increases, reaching 100% at 50mg/l furfural concentration at 120 min, but did not exceed 50% at 200 and 300 mg/l at 240 min reaction time. 2- Increasing the concentration of H2O2 from 250 to 500 mg/l increased furfural removal from 40 to 60%. High concentrations of H2O2 (more than 500mg/l) act as a radical scavenger. 3- The degradation of furfural reached 100% after 90 min exposure time using two UV lamps, where it reached 60% using one lamp after 240 min exposure time. 4- The rate of furfural degradation k increased as the pH and initial concentration of furfural decreased, but different H2O2concentrations indicated no significant effects on the reaction rate. 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